Turning of a propulsion unit

ABSTRACT

The present application is a method and apparatus for moving and steering a vessel traveling in water. The arrangement for moving and steering a vessel includes a propulsion unit having a chamber positioned outside the vessel equipment for rotating a propeller arranged in connection with the chamber, and a shaft means connected to the chamber for supporting the chamber in a rotatable manner at the hull of the vessel. At least one hydraulic motor if used for turning the shaft means in relation to the hull of the vessel for steering the vessel. The arrangement also includes a means for altering the rotational displacement of the hydraulic engine.

THE FIELD OF THE INVENTION

The present invention relates to a propeller operating arrangement forvessels used in waterborne traffic, and in particular to a propelleroperating arrangement which includes a propulsion unit which can beturned in relation to the hull of the vessel and, thus, also can be usedfor steering the vessel. The invention also relates to a method formoving and steering a vessel travelling in water.

THE BACKGROUND TO THE INVENTION

Various ships or similar vessels (such as passenger ships and ferries,cargo vessels, lighters, oil tankers, ice-breakers, off-shore vessels,navy vessels etc.) are moved in most cases by means of the thrust orpulling force of a rotatable propeller or several propellers.Traditionally, vessels have been steered by means of separate rudderequipment.

Traditionally, propeller operating or rotation systems have beenimplemented in such a way that the drive device for the propeller shaft,such as a diesel, gas or electric engine, is positioned inside the hullof the vessel, from where the propeller shaft is led via a lead-throughthat has been sealed to render it watertight to outside the hull of thevessel. The propeller itself is situated at the other end, i.e., the endwhich extends outside the vessel, of the propeller shaft which isconnected either directly to the engine or to a possible gearbox. Thissolution is employed in the majority of all vessels used in waterbornetraffic in order to obtain the power required for moving them.

Later on vessels have been fitted with propeller units in which thedirection of the thrust or pulling force produced by the propeller canbe altered. In these, the equipment which creates the propulsion in thepropeller shaft (ordinarily an electric engine) and a possible gearboxcan be positioned outside the hull of the vessel inside a specialchamber supported to turn in relation to the hull. According to anotheralternative, the propulsion is led by means of angle transmissions anddrive shafts from the engine inside the hull of the vessel to inside thechamber supported to turn, which is outside the vessel (e.g.,arrangements known as rudder propellers).

A propulsion unit fitted with an electric engine inside a chamber isdisclosed in greater detail, e.g., in the applicant's FI patent No.76977. Units of this kind are generally referred to as azimuthingpropulsion units, and, e.g., the applicant in this case suppliesazimuthing units of this type under the trademark AZIPOD. A propulsionunit fitted with a drive engine outside the chamber is presented in,e.g., U.S. Pat. No. 3,452,703 (Becker).

This kind of propulsion unit fitted with a propeller external to thevessel can be turned in relation to the vessel, which means that it canalso be used instead of a separate rudder device for steering thevessel. More precisely, the chamber containing the engine and/or gearboxand any required drive shafts is supported by means of a special pipeshaft or the like to turn in relation to the hull of the ship. The pipeshaft is taken through the bottom of the ship.

In addition to the benefits obtained through the omitting of the longpropeller shaft and separate rudder device, the azimuthing propulsionunit in particular has been found to provide a fundamental improvementin the steerability of the vessel as well. The energy economy of thevessel has also been found to have been rendered more efficient. The useof azimuthing propulsion units in various vessels designed forwaterborne traffic has indeed become more common in recent years, and itis assumed that their popularity will continue to grow.

In the known solutions, the turning arrangement of the propulsion unithas generally been implemented so that a gear rim or the like turningrim has been attached to the pipe shaft. constituting the unit's turningshaft. This rim is rotated by means of hydraulic motors adapted toco-operate with the unit. The liquid pressure and flow required by thehydraulic motors is usually generated by means of pumps rotated byelectric engines. The rotational motion of the rim is also halted andheld in the halted position whenever no control movement is performed inthe common solution by means of the same hydraulic motors. For thisreason, there is constantly the operating pressure maintained by thepumps inside the hydraulic system, also when the vessel is drivenstraight ahead.

A hydraulic turning system is used, inter alia, since that hydraulicsmake it possible to produce the relatively large torque required forturning the propulsion unit at a relatively low speed of rotation at thesame time as turning and steering the vessel by means of hydraulics canbe controlled easily and relatively precisely with the aid oftraditional valve machinery and similar hydraulic components. As wasalready mentioned earlier, one feature which have been obtained with ahydraulic system has been that such a system permits the turningmovement of the propulsion unit's shaft to be halted quickly andprecisely at the desired position, and this position can then be held,something which has been regarded as an important feature as regardssteering a vessel.

According to one known solution, four hydraulic motors have beenpositioned in connection with a turning rim. Correspondingly, theoperating machinery which produces the hydraulic pressure required inthe engines comprises four hydraulic pumps and the electric enginesrotating them. The hydraulic motors are adapted to two separatehydraulic circuits in order to enhance the operating reliability of theturning equipment, so that both circuits have their own operatingmachinery which creates hydraulic pressure (a so-called tandemstructure) Both circuits contain two pumps and two drive engines turningthem, usually with an output of 125 kW, and so the system in itsentirety comprises four 125 kW electric engines. This total output issufficient to produce an adequate turning speed and torque for steeringoperations both at sea and in ports. In the open sea and at normaltravelling speed, a greater torque is required and, at the same time, aturning speed of approx. 3.5 to 5.0 degrees a second (°/s) will usuallysuffice for the propulsion unit when sailing in open water. In ports,and in particular when sailing to the quay, a vessel's manageability and“agility” are more important features. Then a greater turning speed isrequired and, at the same time, the need for torque is not as great aswhen sailing in sea conditions and at higher speeds. For ports and othersuch steering situations, a speed of approx. 5.0 to 7.5 degrees a secondis generally regarded as an adequate turning speed for a propulsionunit. In the known technology, the turning speed of the propulsion unithas been altered by altering the number of running pumps, i.e.,. byswitching pumps on/off as required.

The reason why four 125 kW engines (two per circuit) are used in thevessels instead of two 250 kW engines (one per circuit) can be explainedby safety considerations: in black-out situations the vessel's emergencysystems are able to feed sufficient power into 125 kW engines but wouldno longer be able to feed 250 kW engines, which would cause the vesselto become unsteerable.

SUMMARY OF THE INVENTION

In the known hydraulic solution, which has been found to be effectiveand dependable in itself, a number of drawbacks have, however, beendetected. In order to obtain an adequate level of reliability and owingto the aforesaid dimensioning of the emergency systems, the vessels haveto be fitted with an expensive and complicated hydraulics systemconsisting of several electric engines and hydraulic pumps and thecomponents which these require (such as hydraulic pipes and valves,electric cables, control devices etc.). The installation of these,monitoring of their condition and maintenance call for a considerableamount of work. In the tandem system according to prior art, part of thebenefit in efficiency of use of space and in the simplification of thehydraulics which has been obtained by means of an external propulsionunit, and an azimuthing propulsion unit in particular, is lost.

One drawback of the hydraulic systems is also the fact that they areknown to have a tendency to leak/drip oil or similar hydraulic fluidinto their surroundings, in particular from tubes and variousconnections and seal surfaces. This causes both a tidiness problem andalso a safety risk. The internal pressure of the hydraulic system isalso relatively high, and thereby the breakage of, e.g., a hydraulictube can cause a major safety risk. When it is running, a hydraulicsystem is also noisy, and this has an effect, inter alia, on the workingconditions of the operating personnel. The noise is continuous, sincethe system has to be switched on throughout the time when the vessel isin motion. In order to minimize these disadvantages, it should bepossible to obtain a solution for reducing the number of hydrauliccomponents and in particular various pipes, tubes and connections, andpumps and their operating engines.

Furthermore, in the known solution, the speed of the turning movement ofthe propulsion unit can be influenced only by altering the volume flowrate (the volume flow rate of the pumps) of the liquid pumped into thesystem, which is done either by altering the number of engines used andthereby of the pumps pumping the hydraulic fluid or the speed ofrevolutions of the engines. However, there are situations in which thepossibility of a considerably wider range of turning speeds of the unitor even of a stepless turning speed would be desirable.

The purpose of the present invention is to eliminate the drawbacks ofthe known technology and to obtain a new, improved solution for turninga propulsion unit in relation to the hull of the vessel.

One objective of the invention is to obtain a solution in which thenumber of components in the hydraulic system can be reduced withoutcompromising on turning speed, usability and the reliability of thesystem.

One objective of the invention is to obtain a solution whereby theoverall economy of the propulsion unit's hydraulic turning machinery isimproved compared to the known solutions.

One objective of the invention is to obtain a solution by means of whichthe maximum power requirement of the turning machinery can be reduced.

One objective of the invention is to obtain a solution by means of whichthe noise level of the propulsion unit's turning machinery can bereduced compared to the known solutions.

One objective of the invention is to obtain a solution by means of whichthe turning speed of the propulsion unit can be altered and/orcontrolled in a new way.

The present invention which obtains these objectives is based on thebasic realization that the turning speed of the propulsion unit can becontrolled by altering the rotational displacement of the hydraulicmotors which turn the propulsion unit. More precisely, the arrangementaccording to the invention is characterized in particular by what isdisclosed in the characterizing portion in enclosed independent claim 1.

The method according to the invention is characterized by what isdisclosed in the characterizing portion in enclosed independent claim 7.

According to advantageous embodiments of the present invention, themeans for altering the rotational displacement comprise a two-speedvalve, a three-speed valve or the like valve fitted in connection withthe hydraulic motor which valve can be used to alter the displacement ofthe motor, advantageously a radial piston motor. Said means for alteringthe displacement of the hydraulic motor can also be integrated into thehydraulic motor itself. According to an embodiment which is regarded asadvantageous, the system comprises two hydraulic pumps and electricmotor drives arranged to rotate them, and four hydraulic radial pistonmotors arranged so that their displacement can be altered, which motorshave been arranged to rotate the turning rim arranged at the propulsionunit's shaft means. The operating equipment of the hydraulic motor'spower input unit can include a frequency transformer. The adjustment ofthe turning speed of the propulsion unit's shaft means can also bearranged to be stepless.

According to one embodiment which is regarded as advantageous, thedisplacement of the hydraulic motor is altered in a ratio of 2:3.

The turning speed of the shaft means can also be adjusted, in additionto altering the rotational displacement of the hydraulic motor, byadjusting the power input and/or volume flow rate of the pumps in thehydraulic system which operates the hydraulic motor.

The present invention provides a number of significant advantages. Itallows the number of required components, such as pumps, their operatingdevices and hydraulic pipings and the connections between these to bereduced. The same maximum turning speed can be obtained with half of theelectric power which is required in solutions according to prior art.The required amount of hydraulic medium can also be reduced. Thepressure level of the system can also be reduced. The omittedcomponents, smaller amount of medium and lower pressure level reduce thenoise level of the system. The turning solution disclosed provides apropulsion unit turning arrangement that can be adjusted, in a versatilemanner, with respect to the speed and which arrangement is implementedwith fewer components and lower costs than before.

The invention and its other objects and advantages are described ingreater detail in the following exemplifying disclosure with referencealso to the enclosed drawing, where the corresponding reference numbersin the various Figures refer to corresponding features.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 discloses a ship and a propulsion unit installed therein,

FIG. 2 discloses a simplified diagrammatic visualization of the turningarrangement of the propulsion unit according to FIG. 1,

FIG. 3 discloses a diagram of a Prior Art solution according to theknown technology,

FIG. 4 discloses a diagram of an arrangement according to the invention,and

FIG. 5 discloses a flowchart for the function of a turning arrangementaccording to the invention.

A DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 discloses an azimuthing propulsion unit 6 fitted to turn inrelation to the hull 9 of a vessel. FIG. 2 discloses, in turn, oneexemplifying embodiment of a hydraulic turning machinery. Moreprecisely, FIG. 2 discloses an azimuthing propulsion unit 6, whichcomprises a watertight chamber 5. Said chamber 5 has been fitted with anelectric motor 1, which can be any kind of known electric motorstructure. Said electric motor 1 is connected via a shaft 2 to apropeller 4 in known manner known per se. According to one alternative,the structure can also comprise a gearbox fitted in said chamber betweensaid electric motor 2 and said propeller 4. In accordance with onealternative (not shown) there are more than one propeller per chamber.In that case, there can be, e.g., two propellers, one at the front ofthe chamber and one at the rear of the chamber.

Said chamber 1 is supported to turn around a vertical axis in relationto the hull 9 of the vessel on an essentially vertical shaft means 8.Said shaft means 8 (such as a hollow pipe shaft) can be of such adiameter that it allows maintenance work to be performed therethrough onthe motor, a possible gearbox and propeller shaft low down in thechamber.

A 360° gear rim 10 or a corresponding turning rim is connected to saidshaft means 8 for transferring, to said shaft means 8, the propulsionrequired for turning the shaft means in relation to the hull 9 of thevessel. When said shaft means 8 is turned, said propulsion unit 6rotates accordingly. In the case disclosed in FIG. 2 the turningmachinery of said gear rim 10 comprises four hydraulic motors 20, whosepower input arrangement is explained in greater detail in connectionwith the description of to FIG. 4.

The hydraulic motors 20 are advantageously so-called radial pistonengine. One such radial piston engine can comprise, e.g., 16 separatepistons moving in a radial direction, whose working strokes have beenarranged in separate phases whereby the liquid flow fed into the motorcauses the gear rim part fitted to the outer rim of said motor 20 torotate and thereby gear rim 10 to rotate. Although the gear rim partadapted to rotate has usually been fitted to the outer rim of said motor20, in which case the structure of the engine will be essentially low,some other solution can also be employed, such as a gear rim arranged atthe other side of the motor. The radial piston engine, which ismanufactured and supplied, inter alia, by the Swedish company known asHägglunds Drives, is as such well known to a person skilled in the artand a solution that is commonly employed for turning propulsion units,and its functioning is thereby not explained here in any greater detail.

FIG. 3 discloses in the form of a diagram a solution according to priorart, which comprises four hydraulic motors 12 which rotate said turningrim 10 and the corresponding four pumps 15 and the required pipeconnections 16 between them. For the sake of clarity, however, the 125kW electric engines (4 in total) which actuate said pumps 15 are notshown. In this twin-circuit, i.e., tandem solution, each parallelhydraulic circuit 13 and 14 comprises two pumps 15 and two electricmotors. The arrangement is such that when the pumps, each of which has adisplacement of 250 cm³/r, are used, each circuit generates an output(liquid flow) which by itself would create a turning speed of 3.75degrees a second, from which it follows that a maximum turning speed forthe propulsion unit of 7.5 degrees a second is obtained in the eventthat all four electric engines are switched on and are activating thecorresponding pump.

FIG. 4 discloses a similar diagram for an arrangement according to thepresent invention. Correspondingly, the solution is of the tandem type,i.e., it comprises two separate identical power feeding circuits orunits 23 and 24. The units each comprise only one pump unit 25 and onlyone 125 kW electric engine. Pump units 23 and 24 in FIG. 4 each generateby themselves an output which, in the system equipped with the hydraulicmotors of the kind presented in FIG. 3, would be able to provide amaximum turning speed of 2.5 degrees a second, i.e., the total turningspeed would be 5 degrees a second. However, this is not a sufficientvalue.

The inventor has been surprised to discover that the required turningspeed, i.e., 7.5 degrees a second, can also be obtained in anarrangement according to FIG. 4, i.e., with only two pump units and byusing only two 125 kW electric engines. This is achieved by altering therotational displacement of said hydraulic motors 20 whereby the sameamount of in-flowing hydraulic medium will bring about a different rateof rotation at said motor 20. The displacement can be altered, e.g., byusing what are known as two-speed valves, three-speed valves, four-speedvalves etc. or a variable-volume hydraulic motor. In the solutionaccording to FIG. 4, the rotational displacement of one pump can be ofthe order of approx. 400 cm³/r, i.e., a total of approx. 800 cm³/r.

In FIG. 4, reference number 22 indicates a two-speed valve fitted to theradial piston motor 20, usually to its side. Said valve 22 is arrangedfor adjusting the position of the dividing spindle of said radial pistonmotor 20 to the desired degree (usually a few millimeters). This affectsthe motor so that the desired number of its pistons moving in a radialdirection are rendered pressureless, and this affects the rotationaldisplacement of the engine. Valves are available, e.g., for a volumealteration ratio of 1:2 (half of the pistons are pressureless), 1:3 (2/3of the pistons are pressureless) and 2:3 (1/3 of the pistons arepressureless) , of which the latter is regarded as particularlyadvantageous in this example, as will be presented a little later. Theprinciple of the multi-speed valve is the same, but it is arranged tomove the said dividing spindle to several different positions, inaccordance with the type declaration of the valve.

In accordance with another possible solution, the motor has in itselfbeen arranged to be of a variable volume. An option of this kind isprovided, e.g., by an axial piston motor, such as a banana engine (thename comes from its banana-like shape) In an axial piston motor, thestroke of the pistons is altered by altering the cam angle of the motorwith the aid of means integrated into the engine. Adjustable axialpiston engines allow stepless adjustment of the hydraulic motor'sdisplacement, and thereby also adjustment of the propulsion unit'sturning speed.

When the displacement of the hydraulic motor is divided, e.g., with a2:3 two-speed valve in a ratio of 2:3, the same amount of hydraulicmedium will provide a rotation speed which is 3:2 compared to the normalsituation. Whereas it was presented above that with the pump unitsaccording to FIG. 4 a turning speed of 5 degrees a second is obtainedwith normal hydraulic motors, a turning speed of 3/2×5°/s=7.5°/s is nowobtained. As was presented above, this value for the turning speed of7.5 degrees a second is considered sufficient.

It must be observed that not all the aforesaid elements are alwaysnecessary in the turning machinery for implementing the invention, butthat some of them can be omitted or replaced with other elements, andthat the arrangement of the operating equipment may deviate from thetwo-circuit solution presented. At its minimum, only one hydraulic motoris required for turning the propulsion unit. It must also be observedthat the aforesaid dimensioning values are presented for illustratingthe invention better, and that engine output values, turning speedvalues and displacement ratios other than those presented can, thus,also be used in the invention.

In accordance with one embodiment of the present invention whichprovides very versatile possibilities for controlling the turning speed,the operating output of the electric motors which operate pumps 25 canbe fed by a frequency transformer (not shown) acting as the powersource. In that case, the turning speed can be adjusted both byadjusting the displacement of said motors 20 and by adjusting the volumeflow rate of the pumps. The operating principle of a frequencytransformer is, as such, a technology known per se to a person skilledin the art, and so there is no need to explain it here otherwise than byremarking that the general main components of a frequency convertercomprise a rectifier, a direct voltage intermediate circuit and aninverter. Frequency converters are generally used nowadays as inputdevices for AC engines, and they are particularly advantageous invarious adjustable electric drives. The most commonly used frequencyconverters are what are known as PWM (Pulse Width Modulation) convertersfitted with voltage intermediate circuits and based on pulse widthmodulation technology. A frequency converter is economical to use, interalia, due to the fact that it can be used for adjusting the turningspeed of the turning machinery, and thereby of shaft 8. In accordancewith one solution, at least two different speeds are in use. Inaccordance with another solution, the turning speed can be adjustedwithin a predetermined speed range, such as within the range 0 tonominal turning speed.

The function of the frequency converter is controlled by means of asuitable control unit (such as a servo control), which is, in turn,connected functionally to a control device, such as a steering wheel, onthe bridge or a similar place, by means of which the vessel's actualsteering commands are issued. The steering commands issued manually withthe steering wheel are converted, e.g., by means of a separate analogueservo into a course command. According to another solution, the steeringcommands are converted by means of a converter connected to the steeringwheel into digital steering signals, which are sent to the control unit.

FIG. 5 shows a flowchart for one embodiment of the turning equipmentaccording to the present invention. In accordance with the invention,the vessel is moved and steered by means of the propulsion unit. Theposition of the propulsion unit can if necessary be observed by means ofa suitable sensor device. If an observation is performed, theinformation provided by the sensor device can be utilized either inanalogue format, or it can if necessary be converted into digitalformat. If no new command for changing course is issued, the position ofthe propulsion unit is maintained in the direction last issued from thebridge. If, through an observation of the position data or otherwise, itbecomes apparent that the course of the vessel needs to be altered bychanging the turning position of the propulsion unit, this can beperformed in one embodiment of the invention automatically by means ofthe vessel's automatic control system (not shown).

Whenever the vessel has to be turned, the command for this is issued tothe vessel's control system, such as a processor-controlled controlunit. The command is processed in the control system in a predeterminedfashion. After processing, the control unit issues a command to thepropulsion unit's turning machinery. The function of the electric motorswhich operate the pumps and possibly also the number of motors to beused are controlled, e.g., by controlling the function of the electricpower source, after which the desired rotation of the electric motorcauses the propulsion unit to turn via the turning machinery in thedesired manner, and the vessel alters its course accordingly. A turningspeed suitable for the circumstances can also be selected from thebridge. The turning speed of the propulsion unit's shaft can also beadjusted either in degrees (at its minimum only two speeds, or a numberof different turning speeds) or steplessly. The turning speed command isissued to the equipment which regulates the displacement of thehydraulic motors, which alters the displacement of the hydraulic motorsand thereby the turning speed of the propulsion unit accordingly. Inaccordance with the above, adjustment can also take the form of acombination of the adjustment of the hydraulic motors'displacement andthe pumps'volume flow rate.

The invention has thus resulted in equipment and a method which can beused to obtain a new kind of solution for steering a vessel fitted witha propulsion unit. The solution avoids the drawbacks of the prior art,and also provides an advantage with regard to a simpler structure and asuperior overall economy, convenience of use and operating safety. Itshould be observed that the aforesaid examples of embodiments of theinvention do not limit the scope of protection for the invention asdisclosed in the claims, but that the claims are intended to cover allmodifications, equivalencies and alternatives within the spirit andscope of the invention, as specified in the appended claims.

What is claimed is:
 1. An arrangement for moving and steering a vesseltraveling in water, said arrangement comprising: a propulsion unit (6)comprising a chamber (5) positioned outside the vessel, equipment forrotating a propeller (4) arranged in connection with said chamber, and ashaft means (8) connected to said chamber (5) for supporting saidchamber, in a rotatable manner, at the hull (9) of said vessel, at leastone hydraulic motor (20) for turning said shaft means (8) in relation tothe hull (9) of said vessel for steering said vessel, wherein thearrangement comprises means (22) for variably altering the displacementvolume of the hydraulic motor (20).
 2. An arrangement according to claim1, wherein said means for altering the displacement volume comprise atwo-speed valve (22), three-speed valve or a valve providing a highernumber of motor speeds, arranged in the connection with said hydraulicmotor (20).
 3. An arrangement according to claim 1, wherein said meansfor altering the displacement volume of the hydraulic motor areintegrated into said hydraulic motor (20).
 4. An arrangement accordingto claim 1, further comprising two hydraulic pumps (23, 24) and electricmotor drives arranged to rotate them, and four hydraulic radial pistonmotors (20) arranged so that their displacement volume can be altered,which motors are arranged to rotate a turning rim (10) arranged in saidshaft means (8).
 5. An arrangement according to claim 1, wherein controlmeans for the hydraulic motor's (20) power input unit (23, 24) includesa frequency transformer.
 6. An arrangement according to claim 1, whereinthe adjustment of the turning speed of the shaft means (8) is arrangedto be stepless.
 7. A method for moving and steering a vessel travelingin water, in which method the vessel is moved using a propulsion unit(6), which comprises a chamber (5) positioned outside the vessel,equipment positioned inside the chamber for rotating a propeller (4)arranged in connection with said chamber, and a shaft means (8)connected to said chamber for supporting said chamber, in a rotatablemanner, to the hull (9) of said vessel, the shaft unit (8) is turned, byat least one hydraulic motor (20), in relation to said hull (9) of saidvessel for steering said vessel, wherein the turning speed of said shaftmeans (8) in relation to said hull (9) is altered by variably alteringthe displacement volume of said at least one hydraulic motor (20).
 8. Amethod according to claim 7, wherein the displacement volume of saidhydraulic motor (20) is altered by means of a two-speed valve (22), athree-speed valve, a four-speed valve or valve allowing for more speeds.9. A method according to claim 7, wherein the displacement volume of thesaid hydraulic motor (20) is altered in a ratio of 2:3.
 10. A methodaccording to claim 7, wherein the turning speed of said shaft means (8)is controlled, in addition to controlling the displacement volume ofsaid hydraulic motor (20), by controlling at least one of the electricinput and volume flow rate of the pumps (25) of the hydraulic system(23, 24) which operates at least one of said hydraulic motors (20).